Field of the Invention
The present invention relates to a battery management technology, and more particularly, to an apparatus and a method for calculating a degradation degree by measuring a change rate of voltage of a battery.
Description of Related Art
Generally, vehicle mileage is affected by a capacity and/or a state of a battery. However, when the battery is continuously used, the capacity of the battery degrades. When the degradation of the battery occurs, even though the same state of charge (SOC) is displayed, mileage reduction and power reduction for acceleration occur.
The determination regarding the extent of degradation of the battery is based on a method for measuring internal resistance. For example, a battery is connected to an apparatus for measuring internal resistance or a method for measuring internal resistance using an apparatus for measuring internal resistance. Conversely, the determination regarding the extent of degradation of the battery is based on a method for determining a degradation state of a battery in response to an increased degree of internal resistance by estimating the internal resistance based on a modeling analysis on a voltage output of a battery to an input current thereof.
However, it is difficult to separate the battery when measuring the internal resistance of the battery when the battery mounted within the vehicle. Further, the increase in the internal resistance of the battery occurs due to the degradation in capacity and the degradation in power, and therefore, the determination on the internal resistance of the battery may be inappropriate to determine degradation in capacity in eco-friendly vehicles. An example of the eco-friendly vehicles may include an electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), etc.
Further, the degradation of a battery under the condition which the battery is specialized for eco-friendly vehicles is measured when the battery is charged with a constant current and includes a feature that reduces the charging capacity of a specific voltage region. However, the calculation is limited since the calculation is made in a specific temperature region. In other words, a calculation condition having a slow charging region which is constant low current charging and a voltage detection region are wide and the calculation condition does not reflect voltage characteristics based on temperature change. Further, the method compares current integrated quantities in the specific voltage region and therefore the calculation accuracy may sensitively react to an error of a sensor which occurs during the current integration.